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<p>方法<code><strong>has()</strong></code> 返回一个bool值，用来表明map 中是否存在指定元素.</p>
<h2 id="语法">语法</h2>
<pre><code class="language-javascript"><code><em>myMap</em>.has(key);</code></code></pre>
<h3 id="参数">参数</h3>
<dl>
<dt>key</dt>
<dd>必填. 用来检测是否存在指定元素的键值.</dd>
</dl>
<h3 id="返回值">返回值</h3>
<dl>
<dt>Boolean</dt>
<dd>如果指定元素存在于Map中，则返回true。其他情况返回false</dd>
</dl>
<h2 id="案例">案例</h2>
<h3 id="使用has方法">使用has方法</h3>
<pre><code  class="language-javascript">var myMap = new Map();
myMap.set("bar", "foo");

myMap.has("bar");  // returns true
myMap.has("baz");  // returns false
</code></pre>
<h2 id="规范">规范</h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">Specification</th>
<th scope="col">Status</th>
<th scope="col">Comment</th>
</tr>
<tr>
<td><a class="external" href="https://www.ecma-international.org/ecma-262/6.0/#sec-map.prototype.has" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">Map.prototype.has</small></a></td>
<td><span class="spec-Standard">Standard</span></td>
<td>Initial definition.</td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
<p></p><div class="blockIndicator warning"><strong><a class="external" href="https://github.com/mdn/browser-compat-data" rel="noopener">We're converting our compatibility data into a machine-readable JSON format</a></strong>.
            This compatibility table still uses the old format,
            because we haven't yet converted the data it contains.
            <strong><a class="new" href="/zh-CN/docs/MDN/Contribute/Structures/Compatibility_tables" rel="nofollow">Find out how you can help!</a></strong></div>
<div class="htab">
<a id="AutoCompatibilityTable" name="AutoCompatibilityTable"></a>
<ul>
<li class="selected"><a>Desktop</a></li>
<li><a>Mobile</a></li>
</ul>
</div><p></p>
<div id="compat-desktop">
<table class="compat-table">
<tbody>
<tr>
<th>浏览器</th>
<th>Chrome谷歌</th>
<th>Firefox (Gecko)火狐</th>
<th>Internet Explorer</th>
<th>Opera</th>
<th>Safari</th>
</tr>
<tr>
<td>兼容版本</td>
<td>38</td>
<td><a href="/en-US/Firefox/Releases/13" title="Released on 2012-06-05.">13.0</a> (13.0)</td>
<td>11</td>
<td>25</td>
<td>7.1</td>
</tr>
</tbody>
</table>
</div>
<div id="compat-mobile">
<table class="compat-table">
<tbody>
<tr>
<th>浏览器</th>
<th>Android</th>
<th>Chrome for Android</th>
<th>Firefox Mobile (Gecko)</th>
<th>IE Mobile</th>
<th>Opera Mobile</th>
<th>Safari Mobile</th>
</tr>
<tr>
<td>兼容版本</td>
<td><span style="color: #f00;">未实现</span></td>
<td>38</td>
<td>13.0 (13.0)</td>
<td><span style="color: #f00;">未实现</span></td>
<td><span style="color: #f00;">未实现</span></td>
<td>8</td>
</tr>
</tbody>
</table>
</div>
<h2 id="相关链接">相关链接</h2>
<ul>
<li><a href="Reference/Map" title="此页面仍未被本地化, 期待您的翻译!"><code>Map</code></a></li>
<li><a href="Reference/Global_Objects/Map/set" title="此页面仍未被本地化, 期待您的翻译!"><code>Map.prototype.set()</code></a></li>
<li><a href="Reference/Global_Objects/Map/get" title="get() 方法用来获取一个 Map ?对象中指定的元素。"><code>Map.prototype.get()</code></a></li>
</ul>
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